Ignorant question

NewMexiKen needs to purchase filters to protect my Nikon lenses. I understand 81A is recommended. Is this true? How does one determine the size? Is there any brand to seek out? Any brand to avoid? What’s a fair price (ballpark)?

Leave a comment, or email newmexiken at gmail dot com.

Update: A professional photographer recommended 81A multi-coated Hoya warming filters. In fact, he uses them to protect the lens and does not use bothersome lens caps. They’re about $35 each online.